Abstract
The relationship between plant productivity and species richness is one of the most debated and important issues in ecology. Ecologists have found numerous forms of this relationship and its underlying processes. However, theories and proposed drivers have been insufficient to completely explain the observed variation in the forms of this relationship. Here, we developed and validated integration models capable of combining twenty positive or negative processes affecting the relationship. The integration models generated the classic humped, asymptotic, positive, negative and irregular forms and other intermediate forms of the relationship between plant richness and productivity. These forms were linked to one another and varied according to which was considered the dependent variable. The total strengths of the different positive and negative processes are the determinants of the forms of the relationship. Positive processes, such as resource availability and species pool effects, can offset the negative effects of disturbance and competition and change the relationship. This combination method clarifies the reasons for the diverse forms of the relationship and deepens our understanding of the interactions among processes.
Highlights
Plant productivity and species richness are two fundamental properties of plant community structure and functioning
When the first value in each cell in the data columns marked with # in Supplemental Table 1 was substituted into Eqs 10 and 11, the five typical forms of the productivity-species richness relationship (PSRR) with the dynamics of the potential species-pool effect (Sp) and intra-and interspecific competition effects (IICE, b) were derived (Fig. 1)
The combined positive processes regulating the PSRR are dominant at the rising section of the humped PSRR, but combined negative processes act after the intermediate P level, forming the humped pattern
Summary
Plant productivity and species richness are two fundamental properties of plant community structure and functioning. A mechanistic model that identifies plants that are able to use limited soil nutrients with increasing diversity in ecosystems generates a positive form of the SRPR45, whereas a modified multispecies patch-occupancy model reveals negative, positive, and humped forms of the PSRR along disturbance and productivity gradients[46]. Grace et al.[39] structured a causal network of the humped form of the PSRR, in which the humped form was determined to be a dominant form affected by multiple processes, and the causes and patterns of the PSRR were evaluated using structural equation modelling. This formal analysis rejected the humped form of the PSRR and revealed the effects of additional active processes. Trait-based models described by Bayes’ Theorem were used to explain ecosystem restoration with some derived forms of the PSRR and SRPR47
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